Method and device for the uniform bonding of a nonwoven

ABSTRACT

A discontinuous nonwoven formed by a carder or other nonwovens formed from filaments have a higher strength in the longitudinal direction than in the transverse direction on account of the longitudinally oriented lengths of fibres after the hydrodynamic needle punching, for example. This situation can be improved if the pre-bonded nonwoven undergoes a reorientation of the fibres, for example, during a lateral stretching treatment. The fibres already intertwined in the nonwoven are at least partially reoriented, for example, in the transverse direction. In this new position another hydrodynamic bonding treatment can then take place in order to fix this new position. In this way, the nonwoven is generally stronger than would be possible without this reorientation of the fibres.

A nonwoven comprising cut fibres and/or filaments such as also spunbondfibres and/or mixed with natural fibres such as also pulp does not havea uniform distribution of fibres in the longitudinal and transversedirection as a result of the manufacturing conditions. The fibres arestretched substantially in the longitudinal direction of the nonwoven sothat a lower strength after hydrodynamic needle-punching, for example,is obtained in the transverse direction.

The object of the invention is to find a method for obtaining a uniformbonded nonwoven over the surface in both MD and CD directions and thusobtaining a nonwoven having overall increased bonding.

This object is solved in that before, during and/or after a firsthydrodynamic needle-punching and/or a subsequent hydrodynamicneedle-punching over the width, the nonwoven at least partiallyundergoes a forced re-orientation of the fibres and the nonwoven is thensubjected to a further water jet treatment. The re-orientation of thefibres can be produced during lateral stretching, during pressing and/ormerely by surface treatment such as brushing or using water jets alignedsuch that they are laterally obliquely staggered or changing. In thisway, the nonwoven acquires a higher strength than would be possiblewithout this re-orientation of the fibres.

This treatment can take place many times in succession. Care should betaken here to ensure that the nonwoven is uniformly stretched over thewidth, for example, which is achieved if the nonwoven is supported overthe complete surface during stretching, brushing or pressing and theforces acting on the nonwoven act uniformly on the nonwoven over thewidth. Devices for this purpose are known from the textiles field fortreating woven fabric and knitted fabrics.

1. A method for uniform bonding of a nonwoven comprising cut fibresand/or filaments such as also synthetic fibres continuously laidimmediately previously, possibly mixed with natural fibres such as alsopulp, formed for example by a carder or by the air laying method and/orby means of the spun bond method and which fibres are then intertwinedby means of hydrodynamic needle punching, wherein the nonwoven isexposed to a row of water jet bonding treatments on one or both sides,characterised in that before, during and/or after a first hydrodynamicneedle-punching and/or a subsequent hydrodynamic needle-punching overthe width, the nonwoven at least partially undergoes a forcedre-orientation of the fibres and the nonwoven is then subjected to afurther water jet treatment.
 2. The method according to claim 1,characterised in that the nonwoven is stretched over the width topartially re-orientate the fibres.
 3. The method according to claim 1,characterised in that the nonwoven is uniformly pressed over the widthafter a hydrodynamic needle-punching.
 4. The method according to claim1, characterised in that after a hydrodynamic needle punching thenonwoven is brushed uniformly over the width transverse to the directionof transport, for example.
 5. The method according to claim 1,characterised in that after a hydrodynamic needle punching the nonwovenis exposed to water jets uniformly over the width transverse to thedirection of transport.
 6. The method according to claim 1,characterised in that after a hydrodynamic needle punching the nonwovenis exposed to water jets which change transversely to the direction oftransport, perpendicular to the plane of the nonwoven.
 7. The methodaccording to claim 1, characterised in that the nonwoven repeatedlyundergoes successive hydrodynamic needle punching and is then stretchedand/or pressed and/or brushed over the width and needle-punched again.8. The method according to claim 1, characterised in that the stretchingor brushing process is carried out uniformly over the width of thenonwoven when the nonwoven is completely supported over the width. 9.The method according to claim 1, characterised in that another nonwovenis supplied to the nonwoven thus prebonded and both nonwovens are bondedtogether.
 10. An installation for bonding a fibre nonwoven for carryingout the method according to claim 1, characterised in that a device forwater needle punching is combined with a following stretching devicewhich strains the prebonded nonwoven uniformly over the width.
 11. Theinstallation according to claim 10, characterised in that the stretchingdevice is again followed by a water needle punching device and so on.12. The installation for bonding a fibre nonwoven for implementing themethod according to claim 1, characterised in that a device for waterneedle-punching is combined with a following pressing and/or brushingdevice and/or hydrodynamic needle punching device which laterallychanges the fibre orientation of the prebonded nonwoven uniformly overthe width.